Bryostatin is a potential cancer chemotherapeutic agent in clinical trials with positive responses observed for some cancers. Bryostatins are typically isolated from the marine bryozoan Bugula neritina, although those skilled in the art will appreciate that other sources for bryostatins and closely related compounds will exist.
Bryostatins comprise macrocyclic lactones of the structure shown in FIG. 1. Bryostatins derived from nature contain R.sub.1, and R.sub.2 groups selected according to Table 1.